Posts Tagged ‘precipitation’

This year, the Global Information and Early Warning System (GIEWS, a project of the FAO) has brought into public domain a new rainfall and vegetation assessment indicator. The indicator takes the form of maps which describe conditions over blocks of ten days each, with each such block termed a dekad (from the Greek for ‘ten’). Thus we have visual views of divisions of thirds of a month which from a crop cultivation point of view, now lies between the weekly and fortnightly assessments regularly provided by agri-meteorological services.

How to read the colours used in the rainfall anomaly maps.

In 2015, what was quickly called “out of season” rainfall was experienced in most of India during March and April. These conditions carried over into May and that is why the typical contrast between a hot and rainless May and a wet June is not seen.

The panel of maps shows the incidence of normal, below normal and above normal rain during six dekads of May and June. Greens signal above normal, yellows are normal and reds are below normal. The first dekad of May looks like what the second week of June normally does, but for the large above normal zone in the north-central Deccan. The second dekad of May has in this set had the largest number of above normal points, with more rain than usual over the southern peninsula, and over Chhattisgarh, Odisha, West Bengal. Rajasthan and Punjab.

The third dekad of May shows most of India as far below normal. This changes in the first dekad of June, with rain over the eastern coast registering much above normal for the period – Tamil Nadu, Rayalaseema, Andhra Pradesh and Odisha. During the second dekad of June, the divide north and south of the Vindhyas is visible, when northern India and the Gangetic belt continued to experience very hot days whereas over Telengana, Karnataka, Vidarbha and Madhya Maharashtra there was above normal rainfall. During the third dekad of June the picture was almost reversed as the southern states fell below their running rainfall averages.

This panel describes not rainfall but the anomalies (above and below) recorded in received rainfall. At the level of a meteorological sub-division or a river basin, the anomaly maps are a quick and reliable guide for judging the impacts of climate variability on crop phases (preparation, sowing, harvest) and on water stocks.

We now have rain data for four complete weeks from the India Meteorological Department (IMD) and for all the districts that have reported the progress of the monsoon. The overall picture is even more serious than reported earlier because of the falling levels of water in the country’s major reservoirs. [05 to 11 June is the first week. 12 to 18 June is the second week. 19 to 25 June is the third week. 26 June to 02 July is the fourth week.]

Using the new measure of assessing the adequacy of district rainfall (and not the meteorological cgradations that is the IMD standard), in the fourth week of the monsoon the number of districts that reported normal rains in that week (+5% to -5%) is 18; deficient 1 (-6% to -20%) is 31; deficient 2 (-21% and more) is 437; excess 1 (+6% to +20%) is 17; excess 2 (+21% and more) is 113; no data was reported from 25.

Who can you turn to? It’s easier to list those whom you shouldn’t turn to, the top rankers being the country’s press and television wallahs, followed at a not respectable distance by academic commentators, then come the government blokes and bureaucrats (some of whom do know the difference between isobars and salad bars, I’ll give them that). Lurking behind this cacophonous mob are the boffins of the IMD and its associated scientific chapters, a number of whom have got their sums right, but who aren’t given the space and encouragement to tell the great Bharatiya public what said public is yearning to hear simply because regulations forbid, just like it was in 1982, 1957, whenever.

As I may have mentioned before, this is Not A Good Thing. It has taken about a decade of mission mode tutoring (how the UPA bureaucrats loved that phrase, mission mode) to get the media wallahs to see the difference between weather and climate. A few may even have learned to read a wet bulb thermometer and puzzle their way through precipitation charts.

But overall, the profusion of android apps that profess to show cool graphics of clouds with lightning bolts erupting topside so that our humble ‘kisans’ know when it’s going to rain (i.e., by looking down at their screens instead of up at the sky) has not helped the Bharatiya public make more sense of less rain. We have squadrons of Insats and Kalpanas buzzing around the globe beaming pictures from the infra-red to the infra dig back home, every 60 or 90 minutes, busy enough to crash a flickr photo server, but the knowledge that said public can sift from it is sparse, rather like the rainfall over Barmer, Bikaner and Ajmer.

And so it goes, with the waiting for rain replacing with an equal banality waiting for Godot but with a far larger cast of characters, most of them insensible to the greater climatic drama being played out, 30,000 feet overhead, and at the poles, in the vast turquoise swells of the eastern Pacific where a malignant El Nino is brooding, in the Himalayan valleys where crystal zephyrs have been shoved aside by an airborne mat of PM2.5, or to the desiccation that creeps outwards from our towns and cities (7,935 of them, India’s triumphant ‘growth story’) that have enclosed sweeping hectares with cement, asphalt, and the hot foetid belches of factories and air-conditioners. GDP, they have been told, is the great liberator.

And likewise with “Weak rains deliver India’s new Modi government its first economic challenge” that desultorily spies impending delays in the “sowing of main crops such as paddy, corn and sugarcane” and which notes mournfully that “about half of all farms lack irrigation systems” and, even worse, that “reservoir levels are only a fourth of last year’s levels”, this last despite the best efforts, ham-handed though they are, by the Central Water Commission to show India (for Bharat knows) that the reservoir levels in the 85 major reservoirs are low, but not much lower at this point in 2014 than they were in 2013. The GDP bullies dislike contrary numbers, and would go cross-eyed were someone to mischievously mention the existence of 4,845 large dams in India (the blue-ribboned 85 included) whose many water levels we don’t in fact know at all.

And similar vapidity from another quarter, which like its peers cloaks ineptitude with what it takes to be appropriate jargon, “The cumulative rainfall across the country has so far been 45 per cent below the Long Period Average (LPA) for 1951-2000″ and brandishes even more frightful credentials with “a further breakdown of rain data recorded in different meteorological subdivisions shows that normal rainfall has been recorded in only seven of the 36 regions”. But which sere farmer and her wise daughters consider in their universe such things as meteorological subdivisions, when their world is what Balraj Sahni and Nirupa Roy in 1953 showed us so lambently, is no more than ‘do bigha zamin’?

India’s meteorological department has issued its second long range forecast for the 2011 monsoon and has lowered its estimate. Rainfall will be 95% of the 50-year average in the June-September season, which are the monsoon months. In April, the Indian Meteorological Department predicted a monsoon that would be 98% of the long-term average. Normal precipitation is considered to be 96%-104% percent of the long-term average.

India’s agriculture-dependent population has been hoping for adequate rainfall to harvest good quantities of foodgrain and lentils for a second year and bring down inflation, which has led the Reserve Bank of India – the central bank – to raise rates for a 10th time in 15 months. Agriculture accounts for 14% of the economy and a reduced harvest can further lower rural incomes and send food inflation higher than it already is. Inflation in India is the highest among Asia’s major economies.

Bloomberg reported that the wholesale price index in India accelerated 9.06% in May after having increased 8.66% a month earlier, according to official data released on June 14. An index measuring wholesale prices of farm products including milk and lentils rose 8.96% in the week ended June 4 from a year earlier, according to the commerce ministry. India imported record quantities of sugar, lentils and oilseeds in 2009 following the weakest monsoon that year since 1972.

The IMD’s ‘long period’ is 1951-2000 and the department considers probabilities for the country (all-India) and four major regions: north-west India, central India, north-east India and south peninsula. “Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.”

The IMD also employs a six-parameter statistical forecasting system to prepare probability forecasts for five pre-defined rainfall categories. These are deficient (less than 90% of LPA), below normal (90-96% of LPA), normal (96-104% of LPA), above normal (104-110% of LPA) and excess (above 110% of LPA). The forecasted probabilities for the 2011 southwest monsoon season based on this system in percentage for the above 5 categories are 19%, 37%, 37%, 6% and 1%
respectively.

The department’s ‘Summary of the Update Forecasts for 2011 Southwest Monsoon Rainfall’ has said:

(1) Rainfall over the country as a whole for the 2011 southwest monsoon season (June to September) is most likely to be below normal (90-96% of LPA). Quantitatively, monsoon season rainfall for the country as a whole is likely to be 95% of the long period average with a model error of ±4%. The Long period average rainfall over the country as a whole for the period 1951-2000 is 89 cm.

(2) Rainfall over the country as a whole in the month of July 2011 is likely to be 93% of its LPA and that in the month of August is likely to be 94% of LPA both with a model error of ± 9 %.

(3) Over the four broad geographical regions of the country, rainfall for the 2011 Southwest Monsoon Season is likely to be 97% of its LPA over North-West India, 95% of its LPA over North-East India, 95% of its LPA over Central India and 94% of its LPA over South Peninsula, all with a model error of ± 8 %.

According to Reuters, government officials played down concerns that lower rainfall could fan inflation and dampen growth. “There is no need to press the panic button, as June rains are still above normal,” said Shailesh Nayak, the top civil servant in the ministry of earth sciences which controls the country’s weather office.

While rains could be slightly lower than normal in July, India’s chief forecaster said distribution was key. “There are chances the monsoon will pick up after July 15 once it covers the entire country,” said D. Sivananda Pai, director at the state-run National Climate Center. “Don’t go by the numbers, it is the distribution (of the rains) which we are still hoping to be good.” The weather office predicted 27 centimetres of rain in July compared with long-term average rainfall of 29 centimetres, and rains at 24 centimetres in August, when seeds start maturing, compared with long-term averages of 26 centimetres.

Weather office chief Ajit Tyagi remained optimistic. “Ninety five percent is a good forecast,” Tyagi said. “Had it been 90% of the long-term average then it would have been a cause for concern,” he said, adding that in the past slightly below normal monsoon rains had also seen adequate farm output because they were well distributed in the major crop growing regions.

Explaining climatic conditions over the equatorial Pacific and Indian Oceans, the department’s second long range said moderate to strong La Nina conditions that prevailed in the equatorial Pacific during mid-August 2010 to early February 2011 weakened during subsequent months and dissipated to neutral conditions around mid-May 2011. The latest forecasts from a majority of the dynamical and statistical models indicate strong probability for the present ENSO-neutral conditions to continue during the current monsoon season and the remaining part of 2011.

It is important to note that in addition to El Niño and La Niña events, other factors such as the Indian Ocean Sea surface temperatures (SSTs) have also significant influence on India monsoon. However, the latest forecasts do not suggest development of either a positive or a negative Indian Ocean Dipole event during the 2011 monsoon season. In the absence of strong monsoon forcing from both Pacific and Indian Oceans, intraseasonal variation may become more crucial during this southwest monsoon season and lead to increased uncertainty in the monsoon forecasts.

This image, made with data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, reveals high temperatures that contributed to hazardous fire conditions. Image: NASA's Earth Observatory

An afterword about the drought conditions in the USA, centering on the state of Texas, and analysis from the USDA and the World Meteorological Organisation on the extremely dry conditions over northern Europe. This is May 2011 and keeping in mind what happened last year in Russia and Central Asia, we’re going to watch the big crop-growing areas very carefully over the next few weeks.

NASA’s Earth Observatory has said ‘Drought and Heat Create Hazardous Fire Conditions in Texas’ – So far in 2011, more than 1.4 million acres have burned in Texas, a result of some 800 fires. Why is fire activity so extreme in Texas this year? This image reveals high temperatures that contributed to hazardous fire conditions.

Fire needs dry fuel to burn, and weather conditions in March and April turned Texas into a tinderbox. The state began the winter dry season with abundant vegetation, following a moist spring in 2010. But then drought settled over the state in late 2010 and early 2011, culminating in the driest March on record. Many areas received less than 5 percent of their normal rainfall, according to the state climatologist.

In addition to being dry, March and April were warmer than normal. The image shows ground temperatures for April 7 to April 14 compared to long-term average for the week. The red tones indicate that most of Texas was much warmer than average, further drying out the abundant grasses, shrubs, and trees already suffering from a lack of rain.

In its latest World Agricultural Production report (2011 May) the United States Department of Agriculture (USDA), Foreign Agricultural Service has said that the European Union’s (EU) primary wheat and rapeseed region is struggling with dryness. “Dryness prevailed in northern Europe during March and April and continues into May, with far-below-normal precipitation levels and much-above-average temperatures. The high temperatures accelerated plant development so that crops are two to three weeks ahead of normal.”

Dry/drought conditions in Europe. Image: WMO

The report said that dryness is reportedly also interfering with fertilizer uptake by the crops. Both wheat and rapeseed crops need rainfall soon to prevent sharp yield reductions in northern France, northern Germany, England, and western Poland. These affected areas comprise a large portion of the EU’s primary wheat and rapeseed belt.

Planting conditions were generally favorable for EU winter wheat and rapeseed crops last autumn, with adequate soil moisture across most countries, including France and the United Kingdom. In some areas of central Europe however, (including Germany, Hungary, and Romania), rain and wet soils impeded planting, and some fields were likely left unplanted to be sown later with spring crops. Overall, the EU’s winter was rather mild despite one period during late February when minimum temperatures dropped to between minus 15 and minus 20 degrees Celsius for several days in snow-free areas of eastern Germany and western Poland.

The World Meteorological Union, for all its heavyweight authority, has only a couple of paras about the drought conditions in Europe 2011. “A long-lasting dry period persists over large parts of Europe since January 2011. According to data of the Global Precipitation Climatology Centre (GPCC), especially the months February to April 2011 had a considerable rain deficit over large parts of Europe. The 3-month totals over this period ranged between 40 and 80% of the long-term mean 1951-2000 over large areas (see figure below), in many parts of central Europe even below 40%.”

The United Kingdom had extremely dry conditions in March and April, said the WMO, especially in its southeastern parts and experienced its driest March since 1953. The other parts of western and central Europe all had a dry February, March and April. 2011 was up to now one of the driest 10 years in nearly whole Switzerland since 1864. April 2011 was one of the 10 driest April months in Germany since 1881, in continuation of similarly dry April months in 2007, 2009 and 2010. Also the preceding winter 2010/11 was very dry at least in western Europe, causing a very low soil moisture during March and April.